1. Field of the Invention
The present invention relates to a glass plate heating/bending device and, more particularly, to a device suitable as a work device for an automobile window glass.
2. Description of the Prior Art
Heating/bending furnaces are used for curving or bending an automobile window glass or a glass plate for building construction. The heating/bending furnaces of this type support a glass plate on a bending mold, heat and soften the glass plate, and move the glass plate downward by its weight along the surface of the mold. When a comparatively acute bent portion having a small radius of curvature is formed, the temperature within a furnace is controlled and the glass plate is locally heated at a higher temperature along the bending line than for the remaining portion.
A fixed-type heating furnace and a continuous moving-type heating furnace are used as the heating/bending furnaces. In the former furnace, a bending mold is fixed for each glass plate or each glass plate group, and temperature control of the furnace and local heating are performed.
In the latter furnace, a row of a plurality of bending molds are conveyed within the furnace at a constant speed while heating/bending is performed.
In the fixed-type heating furnace, a wire-like electric heater or the like is used as a local heating source. It is comparatively easy to orient the heater or adjust the distance between the heater and the glass surface in accordance with the direction or the radius of curvature of the bending line to be formed on the glass surface. However, the fixed-type heating furnace is not used for a mass production system since it has a considerably low productivity.
The continuous moving-type heating furnace is suitable for mass production. However, since a local heater, such as a gas burner arranged to oppose the moving glass surface, is used for local heating, it is difficult to match the moving path of the local heater with the direction of the bending line set on the glass surface. Particularly since the moving path is formed only parallel to the glass plate convey direction within the furnace, when the direction of the bending line forms an angle with the glass plate convey direction, optimum heating cannot be performed. In other words, it is impossible to heat only a required portion, and an unnecessary portion is heated.
Since the direction or the radius of curvature of the bending line differs depending on the article type of the glass plate to be bent, it is difficult to perform production on a multi article type-small lot base. More particularly, the horizontal position and vertical height of the heating burner must be altered in units of article types, and adjustment therefor considerably degrades the productivity. Particularly when glass plates of different article types can flow in the heating/bending furnace with a random order, continuous production is almost impossible.
A furnace incorporating the features of the two bending furnaces described above can be proposed. More particularly, a wire-like heater for local heating is conveyed parallel to a bending mold which moves within the furnace. With this system, since the wire-like heater for local heating can be arranged along the bending line, optimum heating can be performed, and continuous production is possible when glass plates of the same article type are to be manufactured. However, since the local heating power is obtained using a power supply line, a current collector, and so on, the overall facility becomes complex. In addition, when glass plates are to be manufactured on the multi article type-small lot base, productivity suffers in the same manner as described above.
The present invention has been made in view of these problems, and has as its object to provide a device which enables continuous operation even on a multi article type-small lot base, which can thus provide a considerably high productivity, which can perform position and temperature control of local heating corresponding to an article type quickly and with a high precision, and which can completely work glass plates of different article types that subsequently flow in the heating/bending furnace.